Clean human hair quickly returns to its "dirty" condition due to contact with the environment and due to the buildup of the sebum-secreted by the head. Within a short time (one day to a few days) hair begins to look and feel "dirty". In modern cultures, this look and feel is considered unacceptable requiring the wearer to shampoo their hair frequently. In some countries, the daily shampooing of hair is considered a normal requirement for proper hygiene, whether or not the hair has actually become "dirty".
Shampooing cleans the hair by the removal of environmental contaminants along with the sebum. However, shampooing removes the natural oils and other moisturizing materials. If the hair is of significant length, the hair can be tangled and becomes unmanageable. Once dry, the hair has lost its shine and luster and can be dry and frizzy. Hair can also maintain a static charge when dry that results in "fly-away hair".
As this problem has surfaced in the modern era, solutions have been developed to correct or to minimize the problem from frequent shampooing. The first acceptable solutions entailed the post-shampoo application of hair conditioners and hair rinses, generally while the hair is still wet immediately after shampooing. These conditioners and rinses were left on the hair for a period of time to allow sufficient treatment and then removed by rinsing with water. These solutions have, as late, been deemed inconvenient and time consuming. The solution to this problem has been the incorporation of conditioners into the shampoo itself, thus the advent of "conditioning shampoo".
Shampoos that contain conditioners or conditioning agents have not been completely satisfactory for various reasons. Hair is composed of keratin, a sulfur-containing fibrous protein. The isoelectric point of keratin, and more specifically of hair, is generally in the pH range of 3.24.0. Therefore, at the pH of a typical shampoo (about 5.5-6.5), hair carries a net negative charge. Consequently, cationic polymers due to their positive charge have long been used as conditioners in shampoo formulations, or as a separate treatment, in order to improve the wet and dry combability of the hair. The substantivity of the cationic polymers for negatively charged hair along with film formation facilitates detangling during wet hair combing and a reduction in static flyaway during dry hair combing. Cationic polymers generally also impart softness and suppleness to hair.
When cationic polymers are added to shampoos containing good cleaning anionic surfactants, formation of highly surface active association complexes generally takes place, which imparts improved foam stability to the shampoo but provides poor conditioning. Maximum surface activity and foam stability, or lather, are achieved at near stoichiometric ratios of anionic surfactant: cationic polymer, where the complex is least water soluble. However, cationic conditioners exhibit some incompatibility at these ratios. Compatibility gives a commercially more desirable clear formulation, while incompatibility leads to a haze or precipitation, which is aesthetically less desirable in some formulations. Additionally when cationic surfactants are added as an ingredient in the shampoo, they do not provide optimal overall conditioning to the hair in the area of softness and tend to build up on the hair resulting in an unclean feel.
Nonionic silicones have also been disclosed in patents as a shampoo additive to increase the softness of hair. These patents include U.S. Pat. Nos. 2,826,551, 3,964,500, 4,364,837, and U.K. Patent No. 849,433. Shampoo compositions that contain insoluble silicone conditioners are disclosed in U.S. Pat. Nos. 4,741,855 and 4,788,066. Shampoo compositions containing anionic surfactants dispersed in soluble silicone (along with a cationic polymer with a cationic charge density of 3 meq/k or less and an oily liquid conditioning agent) are disclosed in WO93/08787 and in U.S. Pat. No. 5,573,709.
Other publications disclosing the use of silicone conditioning agents include Japanese Patent Application No. 5672095, Laid Open Jun. 16, 1981, published EPO Application 413 416 and 413 417, both published Feb. 20, 1991.
Oily components have been added to shampoo formulations to improve the luster and shine of hair as disclosed in Japanese Patent Application Abstracts 53[1978]-35902, (54129135) and 62[1987]-327266 (168612).
In spite of these attempts to provide optimal combinations of cleaning ability and hair conditioning, it remains desirable to provide further improved hair conditioning shampoo compositions. For instance, it remains desirable to improve overall conditioning, and especially shine and luster, wet and dry combing, and dry hair feel, of hair treated with shampoo containing silicone and cationic material. For shampoos containing oily materials in combination with cationic materials, it remains desirable to improve overall conditioning:, especially wet combing and detangling, dry combing, and dry hair feel. However merely increasing the level of one or both conditioning ingredients can result in adverse effects such as greasy hair feel and loss of fullness. It is desirable to improve conditioning without suffering from these drawbacks.
It is desirable to provide shampoo compositions and methods for cleaning and conditioning hair which can provide excellent cleaning performance and improved levels of conditioning while minimizing any adverse side effects associated with build-up due to the use of excess conditioning agent.